Wednesday, December 7, 2016

Dirt Bike Engine Oil Seal Replacement Guide

*As always, these instructions are general guides to helping you; always check with your service manual for your machine to make sure that you have a clear understanding of the setup. If you are not experienced with installing parts on your machine, Boss Bearing always recommends taking your machine to a mechanic to ensure proper installation. You can buy the parts through us, save a few bucks, and take them to your local mechanic to be installed!

*It is important to make sure you clean your machine to prevent any problems going forward with the installation.

*Please be sure to follow the instructions thoroughly! If the steps to replacing any parts on your dirt bike are done improperly, this can lead to parts failure or possible injury.


1. Remove the most difficult seals first; the main crank seals. The flywheel and electrical stator must be removed by using a special flywheel puller tool.
To remove the old seal, use a seal puller or flat pick to pull it from the case
Compare old seals with new seals for size accuracy. Install the new one with a seal driver tube until it’s flush with the engine case. 
Reinstall the flywheel and stator.
2. Clutch side seal must be replaced by removing the right engine clutch cover case, along with the clutch basket and primary drive gear.
Remove old seal and compare to new for size accuracy
Install new seal and reassemble the clutch side
3. Clutch arm seals usually are held in by a retaining bolt or snap ring.
Remove the clutch arm actuator to remove and install the new seal
4. The kicker shaft seal must be removed by unbolting the kick starter lever from the shaft.
Remove the old seal and compare it with the new seal, then install it and reinstall the kicker
5. The shifter lever must be removed to replace the shift shaft seal. 
Remove the pinch bolt that’s holding the shifter on. Then remove the shifter and old seal. Install the new seal and the reinstall the shifter.
6. Remove the front sprocket by using the chain and rear brakes to assist with loosening the sprocket/counter shaft nut
Remove the sprocket and any seal guard/shield to get to the old seal. Pull the seal collar from the shaft, then remove the old seal and compare it to the new seal.
Install the new seal and inner seal collar
Reassemble and torque it to OEM specifications